1. Field of the Invention
This invention relates to calibrating apparatus and more particularly to such apparatus for checking the calibration of indicators of the bar graph type as well as for other purposes in connection with control stations.
2. Description of the Prior Art
It has heretofore been proposed to provide electronic controllers of various types including proportional, proportional plus integral, proportional plus integral plus derivative, and proportional plus derivative.
It has been proposed to provide bar graph display panels that have analog displays with digital accuracy for process control and other purposes. Examples of bar graph panels are disclosed in the U.S. patent to Maloney, U.S. Pat. No. 3,973,166 and controls for such a panel are shown in the U.S. patent to Saxon, U.S. Pat. No. 3,967,158.
In my prior application for letters patent of the United States filed July 13, 1977, Ser. No. 815,101 now U.S. Pat. No. 4,110,665, a control circuit for a bar graph display panel is shown which has since been embodied in module form and for which the calibrator of my invention is suitable although not limited in its use to the specific display panel therein disclosed.
Various types of testing and calibrating equipment have heretofore been proposed but none of the devices now available have the versatility and precision of the calibrating device of my invention.